Premium
A study of isolation procedures for multiple infections of Salmonella and Arizona in a wild marsupial, the quokka ( Setonix brachyurus )
Author(s) -
Hart R. P.,
Iveson J. B.,
Bradshaw S. D.,
Speed T. P.
Publication year - 1982
Publication title -
journal of applied bacteriology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.889
H-Index - 156
eISSN - 1365-2672
pISSN - 0021-8847
DOI - 10.1111/j.1365-2672.1982.tb01288.x
Subject(s) - feces , strontium chloride , agar , biology , salmonella , subculture (biology) , population , veterinary medicine , microbiology and biotechnology , isolation (microbiology) , agar plate , strontium , chemistry , bacteria , medicine , genetics , environmental health , organic chemistry
Abstract Rectal swabs and faeces were used in the regular sampling for salmonellas and Arizonas from a heavily‐infected population of a marsupial, the quokka ( Setonix brachyurus ). The media used were strontium selenite A and strontium chloride B enrichment broths, with subculture onto modified bismuth sulphite agar and deoxycholate citrate agar. A study of sampling, enrichment, sub‐culture and colony selection procedures produced an optimal scheme giving high yields but consistent with reasonable economy of time and materials. A three‐swab sample was taken and inoculated into the two enrichment media, and with each enrichment subjected to three subcultures. The absolute efficiency of this procedure was greater than 80% (and confirmed by a serological method), compared with only 67% for a single swab in a single enrichment. Recovery of some serotypes depended on the media used; e.g. Arizonas could not be recovered satisfactorily from strontium chloride B enrichment. Faeces samples were found to be greatly superior to rectal swabs for detecting salmonellas and arizonas but they were less convenient in field studies. In a comparison of rectal swabs and faeces samples where the actual concentration of salmonellas was known, it was found that the efficiency of rectal swabs approached 100% if there were more than 10 3 salmonellas/g faeces, but this declined to approximately 50% if there were 10 2 ‐10 3 salmonellas/g faeces and only 25% if there were less than 10 2 salmonellas/g faeces. A new statistical procedure was introduced for comparing the number of isolations from two methods, and this should be of use in similar methodological studies.